getting panicky?

i'm 16, i'm currently in my first ever relationship and so far it's been so lovely with no arguing or anything like that. i completely trust my girlfriend but for some reason when i kiss her i can get really really shaky and panicky and i'm not sure what triggers that? it's never in front of anyone so it can't be that... i was just wondering if this is a normal thing to happen or if anyone else has experienced that? and any thoughts about causes would be great to help me think about it and explore what might be the issue x